Windchill Matters More

This essay against reporting wind chill factor just popped up again.

The author apparently lives somewhere where issues like 35 deg (Fahrenheit) + windchill are a frequent occurrence (as opposed to 5 deg + windchill). I’ve long said that the number we should stop reporting (or add as a footnote) is air temperature and make wind chill the prominent value. See, here’s the thing: I’m a person, not a pipe or a car or bit of plastic tubing. So what the effective temperature is as perceived by a human is the part that matters. The fact that your car only cares what the air temp is, not the windchill, is true. It’s also less of a concern. There are only a few weeks of the year where it is unclear without checking a forecast whether the air temp is above or below freezing. And your car is far less susceptible to the temperature changes, so precision there is less important. Whereas I need completely different outerwear when it’s 25 [wind chill] than when it’s -5 [wind chill]. 

Now, if the equation is off, that’s something we should look at. In fact, I didn’t know that it assumes you’re moving—I would think that the least-biased representation of wind chill would be on someone just standing there, not generating any significant heat due to motion. 

His argument that the wind chill reading is meaningless because you might be sheltered from the wind or in full sun doesn’t make any sense. The air temp reading also can be off by that same amount if you’re in full sun, and the air temp reading out at the airport is almost inevitably lower than when I’m downtown (and probably higher than if I lived out in the country). This problem of local variability is true whether you’re looking at wind chill or air temp. Mr. Engber is right that it’s not “the same”—I can turn my back to the wind and be a little warmer, whereas if the actual air temp is -40 the only way to keep my nose from freezing is to cover it. But a wind chill of -40 is still a heck of a lot more like an air temp of -40 than it is like an air temp of 0 (even if that is the air temp), even if the equivalence isn’t perfect. And I can’t turn my back if I need to be facing in that direction for whatever reason, at which point I need to cover my nose. 

I also don’t know where he lives, but his assertion that the air temp is relatively steady during the day while the wind has significant daily variability is bogus. We routinely have a 20-degree change in air temp over the course of a day here in MN. On a cloudless day, it could easily drop 30 degrees overnight. 

Personally, I think we should report the wind chill (or heat index, in the summer) as a big, prominent number, and put the air temp in tiny little type off to the side—exactly the inverse of how temperatures are currently reported. For an average person, wind chill or heat index are the more meaningful number. It’s only for a small subset of people that the air temp is as or more important. And the primary time that that is the case is when it is close to the freezing point. If you have outdoor plants (whether garden or farm), you need to know if there is danger of frost. If it is precipitating and you might be on a road, you need to know if there is danger of ice. But the rest of the time? I don’t care what the air temp is. In fact, unless the air temp is between 30 and 40 (Fahrenheit), I literally don’t even need to know.